Core Barrel and Related Drilling Apparatus and Method

ABSTRACT

There is disclosed herein drilling apparatus, in particular for use in the field of oil prospecting, comprising: a first tubular member ( 1, 2, 3 ); a second tubular member ( 6, 7, 8, 9 ) mounted at least partly within the first tubular member so as to be reciprocally free in rotation with respect to the first tubular member about an axis ( 5 ); and a drill bit ( 4 ) operatively connected to one of the first or second tubular members so as to be rotated in response to the one tubular member being turned in order to effect drilling, characterised in that: the drilling apparatus further comprises a restoring member ( 18, 36 ) for applying a forces between the first tubular member and the second tubular member at least in respective first axial directions in response to relative displacement of the first tubular member and the second tubular member in the respective opposite axial directions. Also provided are a tubular assembly and a method of assembling tubular members.

The present invention relates to drilling apparatus. The invention mayfind particular application in a core barrel, in particular for use inthe field of oil prospecting, comprising

-   -   at least one outer tube and a core bit which form an outer        assembly,    -   at least one inner tube and core removal elements which form an        inner assembly, and    -   a holder for holding the inner assembly in the outer assembly        which comprise at least one rolling bearing arranged between        them so that these assemblies are reciprocally free in rotation.

In a customary core barrel, the outer assembly is driven in rotation andthe core bit can therefore dig a core hole. During this time, the innerassembly is held inside the outer assembly in a position fixed in termsof rotation, while being driven axially by the outer assembly.

Core barrels may be made to pass through geological layers, therebygenerating very high levels of vibration in the core drilling equipment.Often, the tools that exist on the market do not withstand these extremeconditions. This is because the axial vibrations increase the risks ofjamming of the system for holding the inner assembly inside the outerassembly. They may also cause damage to the numerous threads which areusually used to join together the outer assembly and inner assembly.Finally, these axial vibrations often have the effect of modifying theaxial position of the inner assembly relative to the outer assemblywhereas, in order for the core to be removed correctly, it is desirablethat the respective depth positions of the core bit and of the coreremoval elements are appropriately adjusted.

It would be desirable to develop a core barrel in which theseabove-described vibrations which damage the threads are greatly reduced.It would also be desirable to considerably simplify the core drillingequipment and to reduce as far as possible the number of threads andalso the number of parts. Finally, it would also be desirable to lockthe system for adjusting the axial position of the inner assembly in theouter assembly, so as to prevent any disconnection between these oncethis position has been adjusted.

The present invention has been made in view of the foregoing background.A drilling apparatus according to a first aspect of the presentinvention is defined in claim 1 below.

In one embodiment, the drilling apparatus is realised as a core barrelas indicated in the introduction, and which further comprises at leastone spacer element which is housed inside the outer assembly, bearing onthe one hand against a bearing surface of one of said inner and outerassemblies and on the other hand against the rolling bearing, therestoring member being a spring member that axially biases said rollingbearing away from the bearing surface.

The spring member, which is preferably prestressed, has the effect, whenaxial vibrations of the inner assembly occur, of absorbing thesevibrations and therefore filtering them.

According to one embodiment of the invention, the spacer elementcomprises an upstream tubular part which bears against an aforementionedouter tube, and a downstream tubular part which bears against anaforementioned rolling bearing, said spring member being arrangedbetween these upstream and downstream tubular parts, bearing againsteach of them and acting thereon axially so as to move them apart, thespacer element additionally comprising retaining features which limitthe moving-apart thereof.

The terms upstream and downstream in the context of the presentinvention are to be understood as a function of the core drillingdirection, an upstream position or element being closer to the surfaceand a downstream position or element being closer to the bottom of thecore hole. The spring member advantageously consists of spring washers.The latter are preferably arranged so that all the spring washers exertan elastic stress both in the upstream direction and in the downstreamdirection. Other known spring member can of course be envisaged, forexample a helical spring.

According to one advantageous embodiment of the invention, one of saidupstream and downstream tubular parts has a female tubular end piece andthe other has a male tubular end piece capable of sliding axially insidea cavity of the female tubular end piece, and the spring member ishoused at the bottom of said cavity, bearing against the male end piecepushed into the female end piece. The spacer element is in this way inan advantageously compact form.

Said retaining features, which limit the moving-apart described above,advantageously comprise a plurality of elongate slots provided in theaxial direction in the female tubular end piece and locking elementsfixed to the male tubular end piece so as to protrude radially into saidelongate slots and to lock a predetermined spacing of said tubular partsby bearing against one end of said elongate slots. This arrangementallows a particularly simple and robust installation of the spacerelement.

According to one particularly advantageous embodiment of the invention,said holder comprises two upstream and downstream rolling bearingsplaced around an aforementioned inner tube and housed inside anaforementioned outer tube, the downstream rolling bearing being arrangedbetween a downstream-facing first annular bearing surface of the innertube and an upstream-facing annular stop surface of the outer tube,whereas the upstream rolling bearing is arranged between anupstream-facing second annular bearing surface of the inner tube andsaid spacer element, said first and second annular bearing surfaces ofthe inner tube being located between the two rolling bearings.

The particular arrangement of an inner tube biased axially in thedownstream direction by a spring member and clamped between two rollingbearings makes it possible to eliminate almost all the threads which, inthe prior art, were necessary to ensure the connection between the outerassembly and inner assembly. This results in an item of equipment whichis particularly robust and resistant to vibrations. The inner tuberemains in a very stable position, correctly aligned axially by the tworolling bearings.

Advantageously, said first and second annular bearing surfaces of theaforementioned inner tube are provided on an annular flange whichprotrudes radially therefrom, and this annular flange is clamped betweenthe upstream rolling bearing, spaced apart from the outer assembly underthe spacing action of the spring member of the spacer element, and thedownstream rolling bearing which is retained by the annular stop surfaceof the outer tube.

According to one particular embodiment of the invention, theaforementioned outer tube is composed of two upstream and downstreamsections which are screwed to one another, the spacer element bearsbetween said upstream section and said upstream rolling bearing, and thedownstream section has said annular stop surface on which the downstreamrolling bearing bears. In this way, due to the clamping which resultsfrom screwing these two upstream and downstream sections together, thespring force of the spring member of the spacer element is automaticallyapplied to the inner assembly at a specific value which can bepredetermined.

According to one embodiment of the invention, said inner tube of theinner assembly is held by said holder inside the outer assembly at anupstream end, and, at its downstream end, it has an outer thread capableof cooperating with an inner thread of another inner tube of the innerassembly in order to fix this inner assembly in an axially adjustedmanner in a position of use.

The inner assembly can thus be adjusted to a suitable depth relative tothe outer assembly in order to remove the core, by using just one singleconnecting thread, which greatly reduces the risks of damage andjamming.

Since unscrewing may occur under the effect of the vibrations,advantageously the core barrel additionally comprises a threaded lockingnut, arranged on said outer thread of said downstream end of said innertube, upstream of the other inner tube, and, in said position of use,this locking nut is clamped to a predetermined clamping torque againstsaid other inner tube. Preferably, the core barrel additionallycomprises a locking washer which, in said position of use, is clampedaround said threaded downstream end of said inner tube, between athreaded locking nut and said other inner tube, this locking washerbeing arranged in such a way as to prevent any unscrewing of the nut andof said other inner tube on said threaded downstream end. Such a system,which is effective, safe, compact and easy to use, ensures that theclamping stress of the locking nut is maintained throughout the entirecore drilling process. This stress is constant and permanent throughoutthe entire core drilling process. It therefore ensures the filtration ofthe cyclic stresses associated with the aforementioned axial vibrations,thereby considerably attenuating the risks of wear of the aforementionedconnecting thread due to a mechanical fatigue phenomenon.

Further aspects of the invention are provided by way of a tubularassembly, as defined in claim 15 below, and a method of assemblingtubular members, as defined in claim 18 below.

Other details and particular features of the invention will emerge fromthe description of an exemplary embodiments of the invention, saiddescription being given below by way of example only, with reference tothe appended drawings, in which:-

FIGS. 1A and 1B together show a view in axial section of an embodimentof a core barrel according to the invention;

FIG. 2 shows a view in axial section of a spacer element used in theembodiment of FIGS. 1A and 1B;

FIGS. 3 and 4 show the installation of an embodiment of a system foradjusting the position of the inner assembly relative to the outerassembly of a core barrel according to the invention;

FIG. 5 shows a plan view of a locking washer of the adjustment system ofFIGS. 3 and 4; and

FIG. 6 shows a partial view in axial section of a variant embodiment ofa spacer element as may be used in a core barrel according to theinvention.

In the various figures, identical or analogous elements are denoted bythe same references.

The core barrel shown in FIGS. 1A and 1B comprises an outer assemblyformed of a plurality of outer tubes 1, 2 and 3 which are screwed to oneanother, and of a core bit 4. From the surface, this outer assembly isdriven in rotation about the axis 5. The core barrel additionallycomprises an inner assembly formed of a plurality of inner tubes 6, 7and 8 which are screwed to one another, and of core removal elements 9which are known and are shown schematically. Finally, a holder, in theillustrated example two upstream and downstream roller bearings 10 and11, are provided for holding the inner assembly in the outer assembly.In this way, these assemblies are reciprocally free in rotation, and theinner assembly remains fixed in rotation while the outer assembly turnsabout its axis. It would also be possible to provide more than tworolling bearings, or even just one, between the two assemblies.

According to the example of embodiment shown in FIGS. 1A and 1B, thecore barrel additionally comprises a spacer element 12 which is shown indetail in FIG. 2.

The spacer element 12 is housed inside the outer tube 1. In theillustrated example, it comprises an upstream tubular part 13 whichbears against the outer tube 1 and a downstream tubular part 14 whichbears against the upstream rolling bearing 10. In this example, theupstream tubular part 13 is provided with a female tubular end piece 15while the downstream tubular part 14 has a male tubular end piece 16which is capable of sliding axially inside the cavity 17 of theaforementioned female end piece.

In the illustrated example of embodiment, a spring member 18 formed of aplurality of stacked frustoconical spring washers is housed at thebottom of the cavity 17 of the upstream tubular part 13, bearing againstthe male tubular end piece 16 pushed into the female tubular end piece15.

Retaining features limit the possibilities of moving apart and, in theillustrated case, simultaneously of bringing together the upstream anddownstream tubular parts 13 and 14. These retaining features consisthere of a plurality of elongate slots 19 provided in the axial directionon the female tubular end piece 15, and of locking elements 20, in theform of bolts for example, which are screwed into the male tubular endpiece 16 so as to protrude radially into the elongate slots 19. The endsof the elongate slots 19 serve as a stop for the locking elements 20 andthus limit a moving-apart of the two parts of the spacer element, beyonda predetermined value. A shoulder 35 is provided on the downstreamtubular part 14 so as to prevent the parts 13 and 14 from being broughtcloser together beyond a certain limit.

By virtue of this arrangement, the axial vibrations which may occur asthe core barrel passes through hard geological layers are effectivelyabsorbed and damped by the spacer element.

As can be seen from FIGS. 1A and 1B, the holder for holding the innerassembly in the outer assembly advantageously comprise, as indicatedabove, two upstream and downstream rolling bearings 10 and 11 which areplaced around the inner tube 6, in particular around the upstream endthereof, and are arranged inside the outer tube 1.

In this example of embodiment, the inner tube 6 carries close to itsupstream end an annular flange 21 which protrudes radially therefrom.This flange is clamped between the two rolling bearings 10 and 11. Thedownstream rolling bearing 11 is housed between the downstream-facingannular bearing surface 22 of the flange 21 and an annular stop surface23 of the outer tube 1. The upstream rolling bearing is arranged betweenthe upstream-facing annular bearing surface 24 of the flange 21 and thespacer element 12, in particular the downstream tubular part 14 thereof.The spring member, by exerting its spacing action between the upstreamand downstream tubular parts 13 and 14 of the spacer element, has theeffect of pushing in the downstream direction the two rolling bearings10 and 11 and the flange clamped between them, the downstream rollingbearing 11 being retained by the annular stop surface 23 of the outerassembly.

Thus, in the case where the inner assembly ascends towards the surfaceunder the effect of axial vibrations, it can be imagined that thedownstream rolling bearing 11 may no longer be in contact with theannular stop surface 23 or the annular bearing surface 22, or even risksbeing dislocated due to a disconnection of the elements constitutingthis downstream rolling bearing 11. However, according to the invention,the upstream rolling bearing 10 takes over while, in addition, thespring member tends to oppose this ascent.

As can be seen from FIGS. 1A and 1B, in the illustrated example ofembodiment, the outer tube 1 is composed of two downstream and upstreamsections 25 and 25′. These two sections are joined to one another by arobust thread 26. The downstream section 25 has the upstream-facingannular stop surface 23. By a suitable screwing of these two sections 25and 25′, it is possible to adjust automatically the return force of thespring member 18 to an appropriate specific value.

In the example of embodiment shown in FIGS. 1A, 1B, 3 and 4, the corebarrel comprises, in a known manner, a system for adjusting the depthposition of the inner assembly relative to the outer assembly. At itsupstream end, the inner tube 6 is held by the rolling bearings 10 and 11inside the outer assembly. At its downstream end, it has an outer thread27 capable of cooperating with an inner thread of the next inner tube 7.This arrangement makes it possible to fix the inner assembly at anadjustable depth relative to the outer assembly. It should be notedthat, in this embodiment, there is a single thread, the outer thread 27,for forming the connection between the outer assembly and the innerassembly, and for adjusting the position of use of the core barrel. Thestructure is therefore greatly simplified compared to the core barrelsaccording to the known prior art, which minimises the possibilities fordamage.

The outer thread 27 is preferably specially designed to be on the onehand robust, so as to minimise the risks of wear on the thread, and onthe other hand particularly long, so as to have an extended adjustmentlength for the inner assembly relative to the outer assembly.

In order to prevent any unscrewing from occurring on the adjustmentsystem between the inner tubes 6 and 7 under the effect of thevibrations, it is provided according to the invention to arrange alocking nut 28 which is screwed onto the inner tube 6, upstream of theinner tube 7. Once the position of the inner assembly relative to theouter assembly has been adjusted, it is then possible to screw thelocking nut 28 against the inner tube 7 to a predetermined clampingtorque. This nut substantially prevents any unscrewing of the innertubes 6 and 7 associated with the vibrations, and thus reduces thecauses of damage or breakage of the outer (adjustment) thread 27.

Advantageously, as shown in detail in FIGS. 3 to 5, it is possible toprovide a locking washer 29 which, in the position of use of the corebarrel, is clamped between the locking nut 28 and the upstream end ofthe inner tube 7. This washer is preferably arranged so as to preventany unscrewing of the locking nut 28 and of the inner tube 7. In theillustrated example, the locking nut 28 has peripheral notches 30 andthe upstream end of the inner tube 7 has peripheral notches 31. Thelocking washer 29 has corresponding tabs 32 around its periphery. In thescrewed position, some of the tabs can be folded in the upstreamdirection into the notches 30 and some can be folded in the downstreamdirection into the notches 31, thus preventing any separation movementbetween the locking nut 28 and the inner tube 7.

In order that said washer is secured to the inner tube 6 in the angularposition while remaining free in terms of axial displacement, two innertabs 33 have been added to the washer 29 so as to be housed in two axialrecesses 34 provided for this purpose on the inner tube 6. As soon astabs 32 are engaged in the inner tube 7 and the locking nut 28, theselatter elements 7 and 28 are thus advantageously held in an angularlyfixed manner relative to the inner tube 6.

It has also been found that, with a core barrel as designed according tothe invention, it became possible to eliminate the seals which wereusually required. Even the lubrication of the outer adjustment thread 27has in fact been found to be unnecessary, and therefore a lubricationchamber at this location has turned out to be superfluous. Thistherefore results in an increased reliability of the system, and it isthus possible to suppress the temperature limits for use of the corebarrel in view of the omission of seals made from rubber or plastomermaterial.

It must be understood that the present invention is in no way limited tothe embodiment described above and that many modifications can be madethereto within the scope of the appended claims.

For example, according to one advantageous embodiment of the invention,there can be envisaged a core barrel comprising an additional spacerelement 36, as shown in FIG. 6. The core barrel of FIG. 6 is identicalto the core barrel of FIGS. 1 to 5, except in the respects illustratedin FIG. 6 and as described below.

As stated, the embodiment of FIG. 6 has additional spacer element 36. Inthis example of embodiment, the additional spacer element is a helicalspring. The additional spacer element is to be inserted between thedownstream rolling bearing 11 and the upstream-facing annular stopsurface 23 of the outer tube 1. When the two sections 25 and 25′ of theouter tube 1 are screwed together, the spring is prestressed, whichmakes it possible to produce a vertical force, directed upwards, on thedownstream rolling bearing 11 and to keep the elements of this rollingbearing 11 in compression, so that they remain secured. In the event ofupward axial displacement of the inner assembly, the downstream rollingbearing 11 is accompanied in this displacement and it is not subject toany impact upon once again making contact with the stop surface 23.

Although the above description has been made predominantly with respectto a core barrel, the invention may find application in other drillingapparatus where it is desired to provide axial damping betweenrelatively rotatable tubular members, and in cases where it is desirableto be able to securely adjust the length and/or relative positionbetween threadedly connected tubular members, such as drill stringcomponents and related equipment, for example in a bottom hole assembly.

1-19. (canceled)
 20. A drilling apparatus for oil prospecting,comprising: a first tubular member; a second tubular member mounted atleast partly within the first tubular member so as to be reciprocallyfree in rotation about an axis with respect to the first tubular member;a drill bit operably connected to one of the first or second tubularmembers so as to be rotated in response to the one tubular member beingturned in order to effect drilling; and a spring member for applying aforce between the first tubular member and the second tubular member atleast in a respective first axial direction in response to relativedisplacement of the first tubular member and the second tubular memberin respective opposite axial directions.
 21. The drilling apparatus ofclaim 20, further comprising: an outer assembly formed by the firsttubular member and the drill bit, wherein the first tubular memberincludes at least one outer tube and the drill bit is a core bit; aninner assembly formed by the second tubular member and at least one coreremoval element, wherein the second tubular member includes at least oneinner tube; a holder configured to hold the inner assembly in the outerassembly, the holder including at least one rolling bearing arrangedbetween the inner assembly and the outer assembly so that the inner andouter assemblies are reciprocally free in rotation; and at least onespacer element formed in part by the spring member, wherein the spacerelement is housed inside the outer assembly such that the spacer elementbears against a bearing surface of one of the inner and outer assembliesand the rolling bearing to axially bias the rolling bearing away fromthe bearing surface.
 22. The drilling apparatus of claim 20, wherein thespacer element further comprises: an upstream tubular part that bearsagainst the at least one outer tube; a downstream tubular part thatbears against the rolling bearing, wherein the spring member is arrangedbetween the upstream and downstream tubular parts and bears against theupstream and downstream tubular parts to act axially thereon so as tomove apart the upstream and downstream tubular parts; and retainingfeatures configured to limit the moving-apart of the upstream anddownstream tubular parts.
 23. The drilling apparatus of claim 22,wherein the spring member comprises spring washers.
 24. The drillingapparatus of claim 22, wherein: one of the upstream and downstreamtubular parts includes a female tubular end piece and the other tubularpart includes a male tubular end piece configured to slide axiallyinside a cavity of the female tubular end piece; and the spring memberis housed at a bottom of the cavity such that the spring member bearsagainst the male end piece pushed into the female end piece.
 25. Thedrilling apparatus of claim 24, wherein the retaining features comprise:a plurality of elongate slots extending in the axial direction in thefemale tubular end piece; and locking elements coupled to the maletubular end piece so as to protrude radially into the elongate slots andto limit a spacing of the upstream and downstream tubular parts bybearing against one end of the elongate slots.
 26. The drillingapparatus of claim 21, wherein the holder further comprises an upstreamrolling bearing and a downstream rolling bearing placed around one ofthe inner tubes and housed inside one of the outer tubes, the downstreamrolling bearing being arranged between a downstream-facing first annularbearing surface of the one inner tube and an upstream-facing annularstop surface of the one outer tube, the upstream rolling bearing beingarranged between an upstream-facing second annular bearing surface ofthe one inner tube and the spacer element, the first and second annularbearing surfaces of the one inner tube being located between theupstream and downstream rolling bearings.
 27. The drilling apparatus ofclaim 26, wherein: the first and second annular bearing surfaces of theone inner tube are provided on an annular flange that protrudes radiallytherefrom and is clamped between the upstream and downstream rollingbearings; the upstream rolling bearing is axially spaced apart from theouter assembly by the spring member of the spacer element; and thedownstream rolling bearing is retained by the annular stop surface ofthe one outer tube.
 28. The drilling apparatus of claim 26, wherein: theone outer tube comprises an upstream section and a downstream sectionscrewed to one another; the spacer element bears between the upstreamsection and the upstream rolling bearing; and the downstream sectionincludes the annular stop surface on which the downstream rollingbearing bears, the screwing of the upstream section and the downstreamsection being adjustable to adjust an prestressed spring force of thespring member of the spacer element.
 29. The drilling apparatus of claim26, further comprising an additional spacer element inserted between thedownstream rolling bearing and the upstream-facing annular stop surfaceof the one outer tube.
 30. The drilling apparatus of claim 29, whereinthe additional spacer element is a spring member.
 31. The drillingapparatus of claim 26, wherein: the one inner tube of the inner assemblyis held by the holder at an upstream end; and the one inner tubeincludes an outer thread at a downstream end configured to cooperatewith an inner thread of another inner tube of the inner assembly inorder to fix the inner assembly in an axially adjusted condition. 32.The drilling apparatus of claim 31, further comprising a threadedlocking nut arranged on the outer thread of the downstream end of theone inner tube, wherein the locking nut is clamped against the anotherinner tube when the inner assembly is in said axially adjustedcondition.
 33. The drilling apparatus of claim 31, further comprising alocking washer clamped around the threaded downstream end of the oneinner tube when the inner assembly is in the axially adjusted conditionand located between a threaded locking nut and the another inner tube,wherein the locking washer is arranged to prevent any unscrewing of thelocking nut and of the another inner tube on the threaded downstreamend.
 34. The drilling apparatus of claim 20, wherein the drillingapparatus is a core barrel.
 35. A tubular assembly for oil prospecting,comprising: a first tubular member; a second tubular member threadedpart way onto a threaded portion of the first tubular member, the secondtubular member configured to be threaded further onto or partiallyunthreaded from the first tubular member to adjust the assembled lengthof the first and second tubular members; and a locking nut configured tobe moved to a locking position to prevent the second tubular memberbeing further threaded onto or unthreaded from the first tubular member.36. The tubular assembly of claim 35, further comprising: a lockingwasher including, respectively, corresponding notches or projectionsthereon to engage with projections or recesses on the second tubularmember and the locking nut when the locking nut is moved to the lockingposition to prevent relative rotation between the second tubular member,the locking washer and the locking nut.
 37. The tubular assembly ofclaim 36, wherein: the first tubular member includes recesses thatextend along at least a portion of the length thereof; and the lockingwasher includes inner projections to engage in the recesses when thelocking nut is moved to the locking position to prevent relativerotation between the locking washer and the first tubular member.
 38. Amethod of assembling tubular members for oil prospecting, comprising:threading a first tubular member part way onto a threaded portion of asecond tubular member to obtain a desired assembled length of the firstand second tubular members; and moving a locking nut into a lockingposition to prevent the first tubular member from being further threadedonto or unthreaded from the second tubular member.
 39. The method ofclaim 38, further comprising providing a locking washer, and whereinmoving the locking nut to the locking position prevents further relativerotation between the first tubular member, the locking washer and thelocking nut and/or between the locking washer and the second tubularmember.